Recently, the performance of portable devices has been remarkably increasing. It is desired that power sources of such portable devices are small and have a high capacity. While, the manufacturing of high-capacity batteries becomes difficult as the sizes of the batteries become small.
Patent Literature 1 discloses a battery that includes a small cylindrical metal can and a sealing member for sealing an opening in the metal can. A winding-type electrode group is accommodated in the metal can. The electrode group includes first and second electrodes, and a separator is interposed between the electrodes. The separator projects on an end surface of the electrode group. The separator thus prevents contact between an electrode and the metal can that have different polarities, and prevents a short circuit between an end of one electrode and an end of the other electrode.